A wireless mesh network is a communication network made up of a plurality of wireless devices (i.e., nodes) organized in a mesh topology. In a true wireless mesh network, which may also be referred to as a self-organizing multi-hop network, each device must be capable of routing messages for itself as well as other devices in the network. The concept of messages hopping from node to node through the network is beneficial because lower power RF radios can be used, and yet the mesh network can span a significant physical area delivering messages from one end to the other. High power radios are not needed in a mesh network, in contrast with point-to-point systems which employ remote devices communicating directly to a centralized base-station.
The term ‘self-organizing’ refers to the capability of mesh networks to form alternate paths for messaging between devices and between devices and a data collector, or a bridge or gateway to some higher-level, higher-speed data bus. Having alternate, redundant paths for wireless messages enhances data reliability by ensuring there is at least one alternate path for messages to flow even if another path gets blocked or degrades due to environmental influences or due to interference.
The paths provided from each node to a bridge or gateway are dynamic, meaning the paths can change in response to a path being blocked or a new path being added. For example, when a device node is commissioned it will generate a list of devices (i.e., neighbors) with which it can communicate. This list may be particularly dynamic as the radio frequency (RF) environment and physical space occupied by the network change (e.g., a wall or metal shield is constructed between two devices limiting communication between the devices). Based on the dynamic neighbor list, the network manager associated with the gateway selects parent/child devices which define the communication paths to/from the device to the gateway device. The list of parent/child devices is also dynamic, but typically less dynamic than the neighbor list. Because of these dynamics, the organization of the wireless mesh network is continuously changing.
One method of analyzing the operation of a mesh network is to review the organization of the mesh network based on the neighbor lists, parent-child lists, etc. provided by the network. Changes in the organization of the network are used to diagnose problems associated with the network. Prior art methods of analyzing the list include displaying each node in a diagram with lines connecting neighbors and/or parent-child pairs.
If a wireless device (or devices) is reliant on a single wireless device (or limited number of wireless devices) to route its message to the gateway, a pinch point (or communication bottleneck) may exist in the mesh network. A wireless device may be deemed to be a pinch point if a failure of that device would result in other wireless devices in the network no longer having a route back to the gateway. A pinch point can have several negative impacts on a wireless network.
First, the wireless devices that have to communicate through the pinch point may have decreased communication reliability. Second, bandwidth for the wireless devices that have to communicate through the pinch point may be limited, and network performance may be adversely affected. Third, a wireless device that is a pinch point will consume additional power to transmit the increased message load. This is especially significant in battery-powered devices (resulting in decreased battery life) or devices dependent on energy scavenging (e.g. a solar-powered device).
Pinch points occur due to a variety of circumstances. For example, pinch points can be the result of poor network design or installation, of a constantly changing RF environment, changes in the physical space in which the network is located (which impacts the RF environment), and of wireless devices being taken out of service.
Information as to whether a wireless device is a pinch point is not provided by the wireless devices or by the gateway. In many cases, users of wireless mesh network are unaware that a pinch point exists in the network until one or more of the adverse affects mentioned above occur. At the time that the user detects the adverse affect, he or she may begin to examine and graphically build a diagram of communication links between wireless devices in order to identify pinch points. This process can take anywhere from minutes to hours, depending on the complexity of the wireless mesh network. Once the communication characteristics of the network are mapped and graphed, the user is then able to address the issues (or issues) causing a network pinch point.
A pinch point that has a low battery can be a critical situation. If a wireless device that is a pinch point runs out of power, its radio will cease to function. The wireless mesh network will lose the pinch point device, as well as those other wireless devices that depend on the pinch point to communicate with the gateway.
In other cases, the loss of a particular wireless device due to loss of power may cause another device within the network to become a pinch point. Although the device that becomes a pinch point may still have adequate battery power, negative impact on the performance of the wireless mesh network will still occur.
Wireless devices in wireless mesh networks typically report battery condition to the gateway along with the measured value of the process variable being sensed by the wireless device. If a low battery alert is recognized, a user of the wireless mesh network may prioritize the replacement of the battery based on the importance of the measurement (the process variable value) generated by that wireless device. This prioritization, however, does not take into account whether low battery condition of a particular wireless device causes that wireless device to create a pinch point failure, causes another wireless device within the network to become a pinch point, or both. Thus the user may be unaware that a device with a low battery may place the measurements of other wireless devices at risk.